1. Field of the Invention
This invention relates to a magnetic media processing device for reading magnetic data magnetically recorded on a magnetic media such as a magnetic card to be processed thereby.
2. Description of the Related Art
A conventional magnetic card processing device provided with a function for reading and writing magnetic data on a magnetic card employs a conveyance monitoring method for performing the reading-and-writing process with a high accuracy even though the conveyance speed of the magnetic card varies.
The conventional magnetic card processing device employing the conveyance monitoring method is shown in FIG. 1. Upper and lower pair of rollers 11 and 12 conveying a magnetic card 10 are arranged in a direction of conveyance, and rotated in a predetermined conveyance direction by pulleys 13 fixed on ends of shafts of the rollers which are driven by a motor 14 through a worm, a worm wheel and a belt 15. The motor 14 is controlled to drive the conveyance rollers 11 and 12 and convey the magnetic card 10 in a predetermined direction.
A magnetic head 16 for executing a magnetic process of reading and writing magnetic data is disposed in a middle position of the pair of conveyance rollers 11 to correspond to a magnetic stripe 17 of the magnetic card 10.
Beside the head 16 there are disposed a detection roller 19 of a rotary encoder 18 and the magnetic head 16 on the same line in a width direction of the conveyance direction. The detection roller 19 is pushed by a pusher roller 20 to catch the conveyed magnetic card 10, whereby the roller 19 is rotated by the conveyance of the magnetic card 10.
The detection roller 19 is connected with a slit disc 21 having slits formed on a circumference thereof at predetermined equal intervals each of which is detected by a light projector 22 and a light receiver 23, whereby a pulse signal is generated for each predetermined distance corresponding to a conveyance travel of the magnetic card 10.
A conventional write circuit of the conventional magnetic card processing device is shown in FIG. 2, wherein a signal xe2x80x9caxe2x80x9d from the light receiver 23 of the rotary encoder 18 is processed by an encoder waveform processing circuit (encoder processor) 24 to form a pulse signal xe2x80x9cbxe2x80x9d of a square wave which is applied to a write circuit 25 which generates an output signal xe2x80x9ccxe2x80x9d of writing data synchronized with the pulse signal xe2x80x9cbxe2x80x9d to be written into the magnetic stripe 17 by the magnetic head 16.
A conventional magnetic data reading circuit of the magnetic card processing device is shown in FIG. 3. The signal xe2x80x9caxe2x80x9d from the light receiver 23 of the rotary encoder 18 is converted to the pulse signal xe2x80x9cbxe2x80x9d of square waves by the encoder waveform processing circuit 24 to be outputted to a CPU (central processing unit) 26. A signal read by the magnetic head 16 is amplified by an amplifier 27 to generate an amplified signal xe2x80x9cdxe2x80x9d which is differentiated by a differentiator 28 to detect its peaks. A signal xe2x80x9cexe2x80x9d of the detected peaks is compared with a slice level by a comparator 29, and the read signal xe2x80x9cfxe2x80x9d is applied to the CPU 26. The magnetic head 16, the amplifier 27, the differentiator 28, and the comparator 29 provide a read circuit means of this device.
In the CPU 26 the time lapse of each time xe2x80x9ctcxe2x80x9d of rise and fall of the read signal xe2x80x9cfxe2x80x9d is timed to be stored, the lapse of time xe2x80x9ctdxe2x80x9d of rise of the pulse signal xe2x80x9cbxe2x80x9d from the rotary encoder 18 is timed to be stored, and the movement travel A of the magnetic card 10 between pulses of the pulse signal xe2x80x9cbxe2x80x9d is previously obtained and known, whereby data of distance is made from time components of the data lengths.
In FIG. 3, for instance, a distance (data length) P corresponding to data xe2x80x9cOxe2x80x9d of the read signal xe2x80x9cfxe2x80x9d is computed out by the lapse time tc1 and tc2 of rise and fall of signals before and after the data and lapse time td1, td2, td3 and td4 of the pulse signal xe2x80x9cbxe2x80x9d before and after each time based on the equation (1) below;
P=Axc3x97(td2xe2x88x92tc1)/(td2xe2x88x92td1)+A+Axc3x97(tc2xe2x88x92td3)/(td4xe2x88x92td3)xe2x80x83xe2x80x83(1)
According to this equation, a time length of the read signal corresponding to data xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d may be converted to a distance. This is a conveyance monitoring method, wherein data of xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d is judged after such conversion to the distance, thereby reading data even if the conveyance speed is changed.
This conventional method, however, has the disadvantages below.
When a proper circuit for improving a reading ability about a low output card is installed into the read circuit means (16, 27, 28 and 29), particularly the differential circuit 22, a processing delay of waveforms happens on reading.
As a rapid speed change happens between several bits of the pulse signal xe2x80x9cbxe2x80x9d based on deformation of the card or dirt adhered to the same, an error of the above-described distance conversion becomes enlarged, resulting into reading error at worst.
In FIG. 4, for instance, as a speed change happens in the magnetic card 10 at a point xe2x80x9cxc3x97xe2x80x9d, a time length T2 of the pulse signal xe2x80x9cbxe2x80x9d of the rotary encoder 18 is expressed by the following equation;
T2=td4xe2x88x92td3
wherein an elapse time tc2 of fall of the read signal xe2x80x9cfxe2x80x9d is located in the time length T2.
Accordingly, when the read signal xe2x80x9cfxe2x80x9d before and after of the point xe2x80x9cxc3x97xe2x80x9d is converted into distance, the time length T1 of the pulse signal xe2x80x9cbxe2x80x9d in the distance P1 is represented by the following equation;
T1=td2xe2x88x92td1
Since an elapse time tc1 of the rise of the read signal xe2x80x9cfxe2x80x9d is located in the time length T1, the above described distance P1 is computed out by these elapse data according to the above-mentioned equation (1).
During the time lengths T1 and T2 of the pulse signal xe2x80x9cbxe2x80x9d of the rotary encoder 18, the magnetic card 10 is conveyed by same distance A, and the average speeds of A/T1 an A/T2 are different, whereby the distance by the time xe2x80x9ctxe2x80x9d of the average speed of A/T1 is different from the distance by the time xe2x80x9ctxe2x80x9d of the average speed of A/T2, thereby causing an error in the distance.
When the peaks or the signal xe2x80x9cdxe2x80x9d, viz., the peaks of the signal xe2x80x9cdxe2x80x9d produced from the amplifier 27 are converted into a distance in FIG. 4, the error may be absorbed because it is small. As described above, however, a process delay time xe2x80x9ctaxe2x80x9d for processing waveforms exists in the differentiator 28, and is regarded as time for conveying the magnetic card 10 whereby error of the above-mentioned distance is enlarged.
For instance, in FIG. 4, when the distance conversion is executed by peaks of the signal xe2x80x9cdxe2x80x9d, the error is so small that the distance P1 and P2 are converted as distances corresponding to two pulses (line xe2x80x9cgxe2x80x9d). When the distance conversion is executed by the read signal xe2x80x9cfxe2x80x9d, the above-mentioned process delay time xe2x80x9ctaxe2x80x9d is treated as the time for conveying the magnetic card 10, whereby the error of the distance is enlarged. The distance P1 is converted as a distance for 1.8 pulses (line xe2x80x9chxe2x80x9d) and the distance P2 is converted as a distance for 2.2 pulses, so that error of the distance conversion is large resulting into reading error at worst.
To avoid the process delay of waveforms of the differentiator 28, there may be proposed a read circuit means for correcting the phase into complete 90 degrees by differential, in which an output reduction portion xe2x80x9cyxe2x80x9d appears in processed waveforms of a signal xe2x80x9cjxe2x80x9d of FIG. 5 which is a exact differentiated output, thereby providing a status that a low output card seems to be accessed. When the output decrease portion xe2x80x9cyxe2x80x9d becomes large, one pulse is regarded as two pulses in the succeeding atop, viz. the comparator 29, resulting in wrong reading.
As a result, when the waveform process delay by the read circuit means is tried to be resolved by a circuit, the reading function is lowered and such resolution cannot be performed by the circuit.
It is, therefore, an object of the present invention to provide a magnetic media processing device capable of precisely reading the read data without errors of distance conversion in spite of any rapid speed variation between several bits in a pulse output of an encoder for conveyance monitoring when read data is converted into a distance.
According to this invention, there is provided a magnetic media processing device including an encoder for producing an output for a predetermined distance in a conveyance distance of a magnetic media on conveyance, a read circuit means for reading magnetic data stored in the magnetic media in synchronizing the output from the encoder to be processed as to its waveforms to produce read data, and an arithmetic means for converting a data length to data of a distance based on a time component of a data length of the read data of the read circuit means by employing the output signal from the encoder to read data based on distance data, wherein the arithmetic means compensates the process delay time in a time component of read data produced from the read circuit means when the arithmetic means converts the data length into the data of distance.
According to this invention, when the data length is converted into the data of distance from the time component of the data length of the read data, the process delay time by the read circuit means in the time component of the data length in compensated, viz., subtracted, to be compensated to time of the data length when any process delay does not happen, whereby distance conversion is executed by exact differential. Thus, even if any speed variation happens between several bits in the pulse output of the encoder, distance conversion about the read data may be executed with a high accuracy without generating any errors.